1620561 has 4 divisors (see below), whose sum is σ = 2160752. Its totient is φ = 1080372.

The previous prime is 1620551. The next prime is 1620569. The reversal of 1620561 is 1650261.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1620561 - 2⁶ = 1620497 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1620569) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 270091 + ... + 270096.

It is an arithmetic number, because the mean of its divisors is an integer number (540188).

2^1620561 is an apocalyptic number.

It is an amenable number.

1620561 is a deficient number, since it is larger than the sum of its proper divisors (540191).

1620561 is an equidigital number, since it uses as much as digits as its factorization.

1620561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 540190.

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 1620561 is about 1273.0125686732. The cubic root of 1620561 is about 117.4595847121.

The spelling of 1620561 in words is "one million, six hundred twenty thousand, five hundred sixty-one".